The Benefits of Preimplantation Testing

What Is Preimplantation Testing?

Preimplantation testing refers to the chromosomal or specific gene testing of embryos before implantation. This is done to select embryos that do not carry genetic defects for implantation into the uterus. This allows couples facing high genetic risks during pregnancy to avoid natural miscarriages, prenatal termination, or birth defects caused by genetic diseases. The ultimate goal is to achieve healthy offspring.

The Principle of Preimplantation Testing

By using high-throughput sequencing technology (Next Generation Sequencing, NGS), single-cell whole-genome amplification products are sequenced to obtain thousands of reads (base sequences). These are then compared to reference sequences of the human genome to map the reads onto the genome.

By selecting windows of a certain length, the number of reads within these windows can be counted, thereby serving as the signal value (digital signal) for that window. This signal tends to stabilize as the sequencing depth and window size increase. These windows with stable signal values are the basis for determining chromosomal abnormalities. For a diploid region (or an entire chromosome), if the signal value is 1.5 times the normal value, it can be determined as a duplication (or triploid). If it is 0.5 times the normal value, it can be determined as a deletion (or haploid).

Benefits of Preimplantation Testing

Increased Clinical Pregnancy and Live Birth Rates

Preimplantation testing screens embryos for genetic abnormalities before implantation, thereby excluding embryos carrying genetic diseases or chromosomal anomalies. This helps in selecting healthy embryos for transfer, increasing the chances of successful pregnancy.

Reduced Risk of Early Miscarriage

Preimplantation testing can effectively identify embryos with chromosomal abnormalities, such as numerical or structural anomalies. By excluding these embryos, the risk of transferring unhealthy embryos into the uterus is avoided, significantly reducing the risk of early miscarriage.

Reduction in the Birth of Children with Genetic Defects

Preimplantation testing helps in screening embryos that carry genetic defects or high-risk genes, preventing the implantation of embryos with hereditary diseases such as Thalassemia, Cystic Fibrosis, or Down Syndrome.

Increased Success Rate of Single Embryo Pregnancies

Gene screening before embryo implantation can also effectively increase the success rate of single embryo pregnancies. By selecting the healthiest embryo among multiple embryos, complications associated with multiple pregnancies, such as premature birth, low birth weight, and pregnancy-induced hypertension, can be avoided.